(a) Field of the Invention
The present invention relates to a process for forming a projectile for smooth bore hunting guns. More specifically, it relates to such a process for forming a composite projectile containing a metal part, essentially of lead, which carries out the function of a conventional bullet for smooth bore hunting guns, and a plastic material portion associated therewith, which carries out functions of wad and of flight control element.
(b) Prior Art
Projectiles for smooth bore hunting guns having various forms are known, in particular: spherical bullets; cylindrical bullets of the type called Stendebach; conic-cylindrical bullets of the Brenneke type, etc. All such types of bullets have advantages and disadvantages, but none of them is completely satisfactory, in particular from the ballistic view-point, i.e., from the view-point of precision of the shot. A bullet which has a spherical shape produces the so called "wind" between the bullet and the inside of the bores, as it is necessary that the diameter of the bullet be smaller than the caliber of the narrowest portion of the gun, such wind having a strong negative influence on the ballistic yield. The Stendebach type cylindrical bullets are strongly influenced by the tail wind and turn over in the air with negative consequences to precision, and further have other drawbacks due to their high deformability if they come into collision with foreign bodies before hitting the target. The Brenneke type conic-cylindric bullets are not sufficiently deformable in the direction of the diameter and therefore must be built with lead ribs to improve their stability, but are insufficiently precise due to an unfavorable form coefficient and inadequate stability in their trajectory.
It is to be added that the presently known bullets cannot be fired from throttled barrels or necks because of the danger that the barrels may swell out at the moment of firing. Actually, when the projectile passes through the neck, it has a friction on the inner walls of the barrel and it may be stopped for a very short instant and slowed in its travel along the axis of the barrel.
It has been proposed by some, in order to improve the ballistic yield of known bullets, to provide bullets with a flight control element, which is practically constituted by the wad of the propellant. The known wads have a sealing function with respect to the gases developed by the propellant charge and an amortizing function in the firing phase, since they are interposed between the bullet and the charge. A type of wad which may also act as flight control element for gun bullets is described in British Patent Specification No. 1,348,320. Such wad has a discoid base which seals off the propellant gases, an upper part which is destined to be connected with the bullet, and an intermediate zone provided with a discoid piece and with amortizing means positioned between the discoid piece and the previously named parts. At the moment of firing, the resistance of the wad along the axis of the cartridge is sufficient to cause its foremost portion to penetrate into a recess which is defined in the bullet and to remain firmly connected thereto to accompany it in its flight.
Such a combination of bullet and wad has considerable disadvantages, on one hand because the described wad is not per se adapted to carry out its functions with efficency, and on the other because the way in which it is connected to the bullet at the moment of firing is inefficient and requires an excessive rigidity of the wad itself, and finally because the structure of the wad is not suited to efficient operation as a flight control element.